American Heart Association Says Antioxidant Supplementation May Not Lower Risk of Cardiovascular Disease 28054

American Heart Association Says Antioxidant Supplementation May Not LowerRisk of Cardiovascular Disease

DALLAS--Consumption of a diet rich in food sources of antioxidantsand other cardioprotective agents--not supplementation with antioxidants-is amore likely pathway to prevention of cardiovascular disease (CVD), according toa new Science Advisory released by the American Heart Association (AHA) in theAugust 3 issue of Circulation (110, 5: 637-641, 2004) (www.circulation.org).

While numerous meta-analyses and randomized clinical trials have beenconducted on the relationship between various antioxidants and heart disease,they have typically failed to validate the hypothesis that antioxidantsupplements have a beneficial effect on CVD morbidity and mortality. Further,the studies have differed with regard to subject populations studied, dose andtype (e.g., synthetic or natural) of antioxidants or antioxidant cocktails,study length and study end points. In addition, the studies have historicallybeen conducted on subjects who have had myocardial infarctions or subjects athigh risk for CVD, rather than healthy subjects representative of the generalpopulation, and have been conducted over periods as varied as one year and 12years.

To complicate matters, some studies have shown antioxidant supplements mayhave potentially adverse effects on CVD. For example, one study showedpost-menopausal women with coronary disease receiving hormone replacementtherapy given vitamin E plus vitamin C had an unexpected, significantly higherall-cause mortality rate and a trend for an increased cardiovascular mortalityrate compared with vitamin placebo women (Waters DD et al. "Effects ofhormone replacement therapy and antioxidant vitamin supplements on coronaryatherosclerosis in postmenopausal women: a randomized controlled trial." JAMA.288, 19: 2432-2440, 2002.) (http://jama.ama-assn.org).Similarly, in another study, subjects with angiographically demonstratedcoronary artery disease taking simvastatin/niacin and an antioxidant cocktailincluding vitamin E, beta-carotene, vitamin C and selenium had a 0.7 percentprogression in stenosis (narrowing or constriction of the diameter of a bodilypassage or orifice) after three years, compared with a 0.4 percent regression inthe group on simvastatin/niacin only (Brown BG et al. "Simvastatin andniacin, antioxidant vitamins, or the combination for the prevention of coronarydisease." New Engl J Med. 345, 22:1583-92, 2001.) (www.nejm.org).

In general, the studies showing either positive or negative effects ofantioxidant supplementation on CVD end points are much smaller studies than thelarger clinical trials that have consistently failed to show any beneficialeffects of antioxidant supplements on several CVD end points.

Moreover, the advisory said, CVD risk reduction should be pursued not throughantioxidant supplementation but though long-term consumption of a dietconsistent with AHA Dietary Guidelines (Krauss RM et al. "AHA DietaryGuidelines: revision 2000: a statement for healthcare professionals from theNutrition Committee of the American Heart Association." Circulation.102, 18:2284-99, 2000.) (www.circulation.org)--whichinclude reduction of saturated and trans fats; increase in dietary fiberconsumption; and increased consumption of fruits, vegetables, whole grains,low-fat or nonfat dairy products, fish, legumes, poultry and lean meats--thelong-term maintenance of a healthy body weight by balancing energy intake withregular physical activity, and the attainment of desirable blood cholesterol andlipoprotein profiles and blood pressure levels; however, no consistent datasuggest consuming micronutrients at levels exceeding those provided by a dietarypattern consistent with AHA Dietary Guidelines will confer additional benefitwith regard to CVD risk reduction, the advisory said.

The advisory concluded that, although past clinical trials have notnecessarily ruled out a role for oxidative mechanisms in the pathogenesis ofhuman atherosclerosis, the existing scientific database of epidemiologicalevidence does not justify routine use of antioxidant supplements for preventionand treatment of CVD and called for further research to clarify the relationshipbetween antioxidants and CVD.

"The Council on Responsible Nutrition [CRN] agrees that further researchis needed," said Annette Dickinson, Ph.D., President of CRN, in a statementreleased by CRN. "In the meantime, people whose dietary patterns includethe regular use of antioxidant supplements have no reason to change thosehabits. Antioxidants have been shown to enhance overall immune function, protectthe eyes from cataracts and macular degeneration, slow the progression ofAlzheimer's disease and reduce the risk of some cancers. In addition, while manyof the studies on vitamin E and heart disease have been disappointing, some havebeen positive. The AHA seems to be trying to prematurely close the door onsupplement use, even while more studies continue."